1. Technical Field
The present invention relates to a method for processing a rotor used for a supercharger and the like.
2. Background Art
In a supercharger, a screw compressor, a roots blower, a Lysholm compressor and the like, each rotor includes a shaft member, in the form of a shaft and a rotor portion around the shaft member. The shaft member is made from rigid carbon steel, while the rotor portion is made from aluminium alloy that has excellent processability. In manufacturing the rotor, the shaft member and an aluminium profile portion constituting the rotor portion are integrally attached with each other by methods like shrinkage fit or internal chill.
However, the shrinkage fit method requires aluminium material of high rigidity to be used as the rotor portion. Such aluminium alloy of high rigidity is not only expensive but also has other problems like the difficulty to make it near net shape, low productivity and higher production cost. On the other hand, the internal chill method, though it reduces production cost and allows the near net shape processing, still shows low productivity.